Why and how does our economy depend on growth? I've head this claimed a lot but never understood it.

You buy a stock, create a company, build a house, because you expect it to increase in value and be a worthwhile investment. If growth stops it will be increasingly hard to do this, because all stocks that are still increasing in value will be bought up, until they cannot anymore. So you keep your money. Deflation. System collapse.

OK, that's a rough argument that needs fleshing out. Has the rigorous argument actually been made and is widely accepted by economists or is this just a meme that's accepted and repeated without much basis?

Adam Smith makes the argument well in A Wealth of Nations. Essentially, the only reason to invest is that you expect to earn something above on top of the risk. Then add that up over everybody in the system. They cannot all get something extra, unless there is growth. That growth is spread over everybody as return on investment. So, if there is no growth, then investment stops earning that extra, so there no point in investment, so nobody hires anybody or builds new machines.

Importantly, it's growth in total value, not growth in number of things. Hence, it's okay that growth is infinite without gobbling up the universe - we can always be better. Stuff can always be sexier.

You may invest to meet your basic needs. People used to build a house so they could be sheltered from them elements, not just to flip it.

But houses are already there. Especially when populations are shrinking.

Same goes for food, etc. my point was that not everything has to be for financial gain -- we have basic needs that are higher in the priority stack and will always be there.

About homes specifically - they have a life span too so they eventually have to be rebuilt or, as others have pointed out, maintained.

But who would want to own a company producing food, when owning cash would be a better investment?

There has got to be some ways in which this basic economic assumption is wrong. Like with cars, I can buy a car and when I sell the car it will be worth much less. But I will buy that car anyways because I need a car.

Or for a business perspective, I buy a dairy cow as an investment, when I sell the cow it will be worth much less than what I bought it for, but I don't mind because the cow has provided a steady stream of milk based income over the years.

So in these ways at least, it doesn't seem like economic prosperity is always dependent on growth.

Maybe in some economic circumstances cash might be a better investment or worth more than my dairy cow, but such a circumstance can't last for long because supply and demand affect money too right - so if enough people get rid of their dairy cow for the cash, eventually that would decrease the supply of milk, increasing price which would put me and my milk business back on top again would it not?

Owning a new car seems like a good investment. You get a bit more car than when buying a used car plus you get a bit more status. When prices of cars drop and better means of transportation arrive you would just keep your cash and use an Uber for example.

With the cow I think the problem is that many people would buy a cow to fulfil the basic need so margins would be extremely thin. People would soon stop buying cows again.

I think this would be generally the case in such a situation: Everything would be a commodity and margins would approach zero. You need only very few people to produce commodities. The majority of the population would be unemployed.

This is not a bad outlook per se, my argument is just that our current system needs growth. We would have to gradually adjust the system once we realize that there is now way to create growth any more.

But surely people invest for "maintenance" purposes too, where nothing extra is expected. I invest in maintaining my house. I don't expect any "return" from that investment, besides the roof not collapsing.

Maintenance is obviously limited to the number of things maintained and cannot stop deflation, because costs will be approaching zero due to innovation and competition.

Edit: And you do expect a return. You maintain your house, because it has a value and rent costs money, so you have more house in the future if you maintain it now. Imagine a world were rent and the value of your house is approaching zero, would you maintain it? You would have more house if you just kept your money and rented a house.

OK, so that raises the next question: why do we need to stop deflation?

Because you liquidate all your assets if there is deflation. No companies, no jobs, no food.

Edit: Obviously I am speaking in very extreme terms and ignoring the fact that there is a government acting and that not everything will happen instantly. These are just long-term forces.

Do I? Why? What can I do with all that cash that I got from liquidating my assets? I can't spend it on consumption all at once.

You don't have to, it will be worth more next month. It would be stupid to invest into your retirement fund if cash is increasing in value faster, so you take the cash. It makes total sense individually, but when everybody does it, the system will collapse.

Yes, I can see why a deflationary shock can cause behaviour that is individually rational but destroys the economy in the long term. I do not see why there cannot be a steady state with no growth. Presumably if this is widely accepted by economists there must be a standard textbook reference that you can give me?

I am not an economist and would be interested in such a reference, too.

My guess is that as long as there is even tiny growth, central banks can react with negative interest rates/taxing cash. It will take quite a while until there is no growth at all on the whole world. I think even Western countries have room for growth by mandating green standards.

When less and less growth is possible any more, I imagine we would have to start socializing industries, which reached that point, so they are taken out of the equation. People would then get a basic income and use it to pay for state provided services, which would not deflate, because the state does not have to care about market prices, it can just regulate competition. I think the problem here is more to find the right time for it, not the solution itself.

As I understand it, such a thing is hypothetically possible. However, as long as populations grow and people want change in their lives, it is not desirable.

Then there would be growth. What we were debating was that we need growth, otherwise eventually the described things would happen.

That growth by population growth is not sustainable should be obvious, somebody in here made a good argument why this is true even if we populate the universe.

The problem with this argument is that it mixes global effects and personal effects.

A person could have an appealing investment - for example building a more attractive fruit shop, with better customer service - taking all the sales from the current fruit shop .

But the GDP will remain the same.

You are describing a zero-sum game.

Here's an interesting theoretical argument that growth can't continue forever (not saying this applies now):

"[I]f energy became arbitrarily cheap, someone could buy all of it, and suddenly the activities that comprise the economy would grind to a halt. Food would stop arriving at the plate without energy for purchase, so people would pay attention to this. Someone would be willing to pay more for it. Everyone would. There will be a floor to how low energy prices can go as a fraction of GDP."

http://physics.ucsd.edu/do-the-math/2012

It seems like a similar argument could be made for land.

That doesn't seem to have anything to say about growth.

Well, it does. If there is a limit on how small X can be as a percentage of the total economy (because we value it), and the amount of X that can be produced is finite, this puts a limit on the size of the total economy.

My understanding is that our economic structure and model is based on the expectation of growth fueled by continuous innovation, growing efficiency, growing workers productivity; the pie grows, and the slices become bigger for everybody.

If (when?) that stops, we'll have to change our model. We already have big problems with the pies not getting bigger for a big part of the population.

What living being can survive without growth?

If you mean getting bigger in size, all adults.